Aerosol optical properties at Pasadena, CA during CalNex 2010

Jonathan E. Thompson, Patrick L. Hayes, Jose L. Jimenez, Kouji Adachi, Xiaolu Zhang, Jiumeng Liu, Rodney J. Weber, Peter R. Buseck

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Aerosol optical properties measured at the Pasadena, CA site during the CalNex field campaign in May-June 2010 are summarized. Average measurements of PM 2.5 aerosol extinction, scattering, absorption coefficients, and single scattering albedo (b ext, b scat, b abs and SSA) at λ = 532 nm were 62 Mm -1, 58 Mm -1, 4 Mm -1, and 0.92, respectively. The aerosol optical densities were 5 times lower than during the SCAQS study in 1987, highlighting major progress in PM control in the Los Angeles area in the last two decades. The period May 30-June 8 2010 was characterized by exceptionally high aerosol loading (b ext up to 250 Mm -1). During this period, b ext, b scat, and SSA tended to peak during the mid-morning. Correlation of PM 2.5 b ext, b scat with mass concentration data yielded mass scattering and mass extinction coefficients of 3.5-5.1 m 2 g -1 for 532 nm. Aerosol b abs were compared directly to mass concentration of elemental carbon (EC) yielding a campaign average mass absorption cross section (M.A.C.) of 5.7 ± 1.8 m 2 g -1. TEM analysis of particles suggests soot was often internally mixed or adhering to sulfate and/or organics. Total non-refractory PM 1 mass was a good quantitative indicator of coated soot fraction. Alteration of M.A.C. with mixing/coating state was not detected, however, increases in M.A.C. were linked to the presence of light absorbing, water-soluble organic carbon (WSOC) suggesting a possible role of this material invisible light absorption in the LA basin.

Original languageEnglish
Pages (from-to)190-200
Number of pages11
JournalAtmospheric Environment
StatePublished - Aug 2012


  • Absorption coefficient
  • Absorption enhancement
  • Aerosol optics
  • Albedometer
  • Brown carbon
  • CalNex
  • Direct climate forcing
  • Extinction coefficient
  • Mass absorption cross section
  • Mass scatter efficiency
  • Scattering coefficient
  • Single scatter albedo
  • WSOC


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